Medical injectors and syringes for injecting contrast media into a patient for imaging biological structures are known in the art. For example, U.S. Pat. No. 4,677,980, issued to D. M. Reilly et al. on Jul. 7, 1987, and entitled “Angiographic Injector and Angiographic Syringe for Use Therewith,” which is assigned to the same Assignee as the subject application, discloses an angiographic injector apparatus. The apparatus is designed for injecting contrast media into the vascular system of an animal, in which syringes are rear-loaded into a pressure jacket of the injector. More specifically, the apparatus comprises a rotatable turret which carries a pair of the pressure jackets and which is rotatable so that when one of the pressure jackets, into which a syringe has been rear-loaded, is in an injection position, the other pressure jacket is in a position in which an associated syringe can be rear-loaded. Subsequently, when injection of contrast media from the first syringe is completed, the turret is rotated to move the first syringe to an unloading-loading position, with the second pressure jacket and the syringe concurrently being moved into the injection position.
In the apparatus disclosed in the '980 patent, a drive member of the angiographic injector can be drivingly connected to, or disconnected from, a plunger of a syringe at any point along the path of travel of the syringe plunger by a releasable mechanism. However, for the releasable mechanism to correctly operate, the syringe plunger must be properly oriented to mate with the injector piston. Further, during loading of the syringe on the injector, the syringe must be correctly aligned within a respective pressure jacket to allow the syringe plunger and the injector piston to connect to and disconnect from each other.
An improved apparatus over the '980 patent apparatus is disclosed in U.S. Pat. No. 5,383,858, issued to D. M. Reilly et al. on Jan. 24, 1995, and entitled “Front-Loading Medical Injector and Syringe for Use Therewith,” which is also assigned to the same Assignee as the present application. In the apparatus described in the '858 patent, the syringe is front-loaded onto, in at least one embodiment, a pressure jacket-less injector, overcoming one of the drawbacks of the '980 patent injector apparatus.
The injector described in the '858 patent has a first release mechanism for attaching and releasing the syringe from the injector. In addition, the apparatus includes a second release mechanism that engages and disengages the injector piston from the syringe plunger. Upon rotation of the syringe, the syringe is attached to or released from the injector and, simultaneously, the plunger is attached to or released from the piston. The structure disclosed requires that the syringe be installed on the injector in a specific orientation so that the syringe can releasably engage the injector and, simultaneously, the plunger can releasably engage the piston. In addition, as with the syringe disclosed in the '980 patent, during assembly the syringe plunger must be correctly oriented within the syringe.
Another injector apparatus is disclosed in U.S. Pat. No. 5,300,031, issued to C. Neer et al. on Apr. 5, 1994, and entitled “Apparatus for Injecting Fluid into Animals and Disposable Front Loadable Syringe Therefor.” The '031 patent discloses various embodiments of a pressure-jacketed injector wherein a syringe is loaded into and removed from an injector pressure jacket through an opening provided in the front end of the pressure jacket. To retain the syringe within the pressure jacket, for example, during an injection operation, the front end of the syringe is locked to the front end of the pressure jacket. To correctly connect the syringe to the pressure jacket, the syringe may only be inserted into the pressure jacket in one orientation.
In each example discussed above, the syringe must be connected to the injector in a specific orientation to assure proper syringe mounting. Proper alignment is required to assure that the syringe may be operated properly during a medical imaging procedure. The required orientation, however, hinders rapid attachment and replacement of the syringe. The required orientation may also increase the manufacturing assembly cost and complexity of the syringe.
Accordingly, while the above injector and syringe apparatuses have proven effective, a need has arisen for a simpler front-loading medical injector. More specifically, to facilitate further the loading operation, a need has arisen for a syringe that can be easily connected to the injector without regard for the specific orientation of the syringe and/or syringe plunger. In addition, to simplify assembly of the syringe components, a need has arisen for a syringe with a plunger that does not need to be oriented in a specific relation to the barrel or base of the syringe. Furthermore, to minimize the time required to prepare an injector for an injection procedure, a need has arisen for injectors providing automated features. There is a further need to add automated features which contribute to the safety of the patient, for example, by decreasing the chances of cross-contamination.
Medical fluids are normally packaged in containers or bottles, which have an elastomer bung (or cork) in the top. The bung can be pierced with a conventional needle or a plastic spike to draw fluid from the bottle into the syringe. However it is common practice to simply remove the bung, and draw up fluid into the syringe using a plastic cannula. This practice exposes the fluid to ambient microbes, and allows contamination, and thus increases the risk of undesirable infection of the patient. Certain vented spikes with special microbe filters have been developed to address this problem. However in use, the filling procedure is very tedious, and some fluid is often lost through the filter. Where large volumes are drawn into the syringe according to known methods, it can be very difficult to simultaneously hold the bottle inverted, and draw back the syringe.
Another important requirement when using syringe pumps to inject patients is to ensure that all air is purged from the system, including the tube, before it is connected to the patient. If this is not done, then it is possible that a bubble of air may be injected into the patient which can cause serious illness.
It has also been found that existing injector apparatus and injectors do not have features which discourage inadvertent re-use of syringes and associated tubes and spikes, which can result in the serious hazard of cross infections from one patient to the next.
Luer connectors are found on the outlet of most syringes used in medicine, and are well defined in International Standard ISO594. A locking thread is sometimes found associated with luer connectors, termed “luer locking”, and are particularly used for higher pressure applications, where the thread assists closure and retention of the connections.
Flexible plastic tubing is used in many medical applications for conveying drugs, fluid, contrast etc. between syringes and patients. The tubes are normally manufactured from flexible plastic, with luer connectors bonded to each end to facilitate secure and releasable male and female connections. Connectors are normally moulded from rigid plastic, having a luer outlet, with a cylindrical inlet sized to accept a close interference fit with the relatively soft tube. The tubing is forced over (or inside) the cylindrical inlet end, and is traditionally bonded using solvent or cement adhesive. For higher pressure applications the bond must be very certain and secure to avoid bursting.
On occasions, the tubing may be attached permanently to the syringe, for example to reduce manufacturing costs, reduce the chances of spilling contaminated fluids, or to protect the tip of the syringe from contamination. However bonding directly to syringes is rarely successful or certain because syringes are usually moulded from polypropylene. Some tubing materials are also difficult to bond. Moreover, bonding normally requires the use of powerful solvent cements such as cyclohexanone, or cyanoacrylates, both of which release harmful vapours, and can leave unwanted residues.
In this specification, unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date:    (a) publicly available;    (b) known to the public;    (c) part of common general knowledge; or    (d) known to be relevant to an attempt to solve any problem with which this specification is concerned.